This invention generally relates to electronically controlled motors and to systems, such as heating, ventilating and/or air conditioning systems having motors therein operating according to predetermined parameters which are selected to correspond to the system in which the motor is installed.
While conventional brush-commutated DC motors may have advantageous characteristics, including convenience of changing operation speeds, there may be disadvantages such as brush wear, electrical loss, noise and radio frequency interference caused by sparking between the brushes and the segmented commutator, and overall material cost of the motor. These disadvantages may limit the applicability of such brush-commutated DC motors in many fields, including the refrigeration, heating, ventilating and/or air conditioning (HVAC) fields. Electronically commutated motors, such as brushless DC motors and permanent magnet motors with electronic commutation, have now been developed and generally are believed to have the advantageous characteristics of brush-commutated DC motors without many of the disadvantages thereof while also having other important advantages. Such electronically commutated motors are disclosed in the David M. Erdman U.S. Pat. Nos. 4,015,182 and 4,459,519, for instance. Such electronically commutated motors may be advantageously employed, for instance, in HVAC systems which employ variable speed motors.
Present motors have a variety of features and operational and system parameters which must be adjusted to optimize performance by providing a proper speed-torque characteristic for a particular application. Further, in many system applications, the starting torque and/or speed-torque characteristics of the motors must be predictable and repeatable. In addition, it is desirable that motors be operable at the highest reasonably achievable efficiency consistent with mass production techniques. Known present variable speed motors cannot easily achieve this advantage because it has traditionally been impractical or too costly to minimize the variable effect on motor characteristics caused by manufacturing tolerances of the internal components of the motor. Present concepts and arrangements for adjusting a motor for different applications require circuit changes such as multiple variable resistors in the electronic control for the motor or permanent software changes in an electronic control microprocessor. Both of the aforementioned arrangements are disadvantageous because they require a unique model to be built for calibrating a system which cannot be easily changed and can be quite expensive.
In the specific case of HVAC systems, such systems may include a variety of backup heat ratings, operate in a variety of modes, have variable capacities and be installed in a variety of environments. Both the speed and torque of an electric motor, which affect air flow through the system, are affected by the aforementioned variables. Interfacing a control microprocessor with the necessary information to make these changes often requires complex assemblies, creates possible shock hazards and/or limits the number of available variations.